[4.8.3] Spline Components reset on compile error

This has been posted before but nobody seemed to be able to figure out a repro, but I have found a reliable one after suddenly losing an hour of work to this bug.

1 - Create a BP with a spline component

2 - Place in world and edit the spline

3 - In the Event Graph, make a node that requires a spline component input, such as Get World Location at Spline Distance

4 - Disconnect the spline from the node so it will cause an error on compile

5 - Create a new Spline Component variable, or delete an existing one (a variable, not an actual spline component)

6 - Compile

The BP will turn into a “Bad Blueprint” icon in the world, and all splines will have reset. If you do not create or delete a spline component variable and compile with the Step 3 node disconnected, it won’t cause the “Bad Blueprint” thing and will not reset the splines.

This is a really bad bug because there’s no other way to use splines in Unreal right now and this is a really easy bug to run into if you’re making any sort of complex spline-based BP.

A video of this is attached.

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Hi ,

I attempted to reproduce this but I couldn’t get the blueprint to turn bad by disconnecting the spline variable. Could your upload a small test project that has the issue?

Blank project from 4.8.3 is attached.

It turns out that in order for the node to give an error on compile, you need to have its return value plugged into something that is getting an impulse, like SetActorLocation or something.

But other than that, I was able to reproduce it right away.

link text

Hello ,

I was able to reproduce this issue on our end. I have written up a report (UE-20385) and I have submitted to the developers for further consideration. I will provide updates with any pertinent information as it becomes available. Thank you for your information and time.

Make it a great day

Any update on this issue? I just experienced it today in 4.12.5.

Hello ook,

I have provided a link to the public tracker. Please feel free to use the provided link for future updates.

link: Unreal Engine Issues and Bug Tracker (UE-20385)

Make it a great day